This invention relates to using a synthetic polymer melt spinning process with a high speed draw jet to make drawn filaments. More specifically, the high speed draw jet utilizes the tension created by high velocity air when it impinges a filament threadline to draw the filaments. The filaments can be collected on a screen and bonded together to make a nonwoven fabric or wound up for use in a woven fabric or other end-uses.
Jet devices have been used with synthetic polymer textile filaments for many purposes including drawing, texturing, bulking, crimping, interlacing, etc. For example, spunbond nonwoven fabrics are typically made by melt spinning one or more rows of filaments, drawing the filaments, collecting the random laydown of filaments on a screen, and bonding the filaments together. A method of drawing the filaments is subjecting the row or rows of filaments to a draw jet. The draw jet uses downwardly projected high velocity air to provide tension on the filaments which draws them. As the tension increases, the polymer throughput and filament speed increases. This would lead to increased productivity. However, consuming more air can be expensive. Also, the air may be heated which adds to the expense. In the spunbond process, too much air flow can lead to non-uniformity in the laydown process. Therefore, it would be advantageous to minimize air usage while increasing filament tension. It would be desirable to use a draw jet that can provide high tension to a filament threadline for drawing, while using minimal air at high velocity to increase productivity.
In a first embodiment, the present invention is directed to a draw jet for drawing thermoplastic polymer filaments comprising a drawing slot defined by an entrance member comprising a converging passageway communicating with a continuing passageway, terminating at an outlet portion, a drawing member comprising an inlet portion having a drawing gap width of about 2.0 to about 10 mm communicating with said outlet portion of said entrance member, and at least one air nozzle for directing high speed air onto said filaments in a downstream direction positioned between said outlet portion of said entrance member and said inlet portion of said drawing member, and with a nozzle gap width wherein the gap ratio of said drawing gap width to the combined width of all of said nozzle gaps is from about 1.0 to about 10.
Another embodiment of the present invention is directed to an apparatus for melt spinning thermoplastic polymer filaments comprising a draw jet for drawing thermoplastic polymer filaments comprising a drawing slot defined by an entrance member comprising a converging passageway communicating with a continuing passageway, terminating at an outlet portion, a drawing member comprising an inlet portion having a drawing gap width of about 2.0 to about 10 mm communicating with said outlet portion of said entrance member, and at least one air nozzle for directing high speed air onto said filaments in a downstream direction positioned between said outlet portion of said entrance member and said inlet portion of said drawing member, and with a nozzle gap width wherein the gap ratio of said drawing gap width to the combined width of all of said nozzle gaps is from about 1.0 to about 10.
In another embodiment, the present invention is directed to a process for drawing thermoplastic polymer filaments comprising drawing said filaments by a draw jet having an entrance member comprising a converging passageway communicating with a continuing passageway, terminating at an outlet portion, a drawing member comprising an inlet portion having a drawing gap width of about 2.0 to about 10 mm communicating with said outlet portion of said entrance member, and at least one air nozzle for directing high speed air onto said filaments in a downstream direction positioned between said outlet portion of said entrance member and said inlet portion of said drawing member, and with a nozzle gap width wherein the gap ratio of said drawing gap width to the combined width of all of said nozzle gaps is from about 1.0 to about 10.
In another embodiment, the present invention is directed to a process for melt spinning thermoplastic polymer filaments comprising melting a thermoplastic polymer, spinning said molten thermoplastic polymer through a spinneret and forming filaments and drawing said filaments by a draw jet having an entrance member comprising a converging passageway communicating with a continuing passageway, terminating at an outlet portion, a drawing member comprising an inlet portion having a drawing gap width of about 2.0 to about 10 mm communicating with said outlet portion of said entrance member, and at least one air nozzle for directing high speed air onto said filaments in a downstream direction positioned between said outlet portion of said entrance member and said inlet portion of said drawing member, and with a nozzle gap width wherein the gap ratio of said drawing gap width to the combined width of all of said nozzle gaps is from about 1.0 to about 10, and collecting said drawn filaments on a collection screen to form a nonwoven web.